JP2002002234A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve motion performance by equalizing the stiffness of a block. SOLUTION: A plurality of blocks 18 are disposed around the entire circumference of a tread 14 along the circumferential direction R of the tread 14. The blocks 18 of five types are different mutually in length along the circumferential direction R, and a tread pattern has five kinds of pitches P1, P2, P3, P4, and P5 appropriate to a difference in the length of the block 18. A sipe 28 is installed in the block 18 in such a manner as to extend in the direction crossing the circumferential direction R. The inclined part inclined along the circumferential direction R is formed between the portion of the sipe 28 on the surface side of the block 18 and that of the sipe 28 on the side of a groove bottom, and the length of the inclined part is taken as proportionate to that of the block 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having an improved sipe shape and uniform block rigidity.

[0002]

2. Description of the Related Art Conventionally, as a pneumatic tire for a passenger car, a tire having a block type tread pattern in which blocks are arranged in a tread of a tire serving as a tread portion in contact with a road surface is known. .
It has been known that the performance of a pneumatic tire is greatly influenced by the rigidity of a land portion, which is a block disposed on a tread, and the performance of the pneumatic tire is improved by equalizing the rigidity of the block. Was required. Therefore, by bending the shape of the conventional sipe, which has been linearly formed from the surface of the block toward the groove bottom, into a crank shape, it is possible to suppress the falling of the block divided by the sipe when a large external force is input, thereby suppressing the falling. The rigidity of the block was improved to make the rigidity of the block uniform.

[0003]

On the other hand, the blocks constituting the tread pattern of the tire have at least two or more pitches along the circumferential direction of the tread in order to reduce noise during rolling of the tire. It is common to arrange.

However, conventionally, even when the pitch of the block along the circumferential direction of the tread changes, the length of the inclined portion, which is the bent portion of the crank-shaped sipe, is set to be constant regardless of the change in the pitch. Therefore, it was not possible to obtain a block rigidity, which is a uniform rigidity of the block along the circumferential direction of the tread, and as a result, it was not possible to improve the exercise performance of the tire. An object of the present invention is to provide a pneumatic tire having improved kinetic performance by improving the shape of a sipe and making the block rigidity uniform in consideration of the above facts.

[0005]

A pneumatic tire according to claim 1 is provided with a tread portion which is in contact with a road surface over one round, and a plurality of land portions are arranged along a circumferential direction of the tread portion. A plurality of types of land portions having different lengths along the circumferential direction of the tread portion, extending in a direction intersecting the circumferential direction of the tread portion, and a land portion. A sipe having an inclined portion between the surface side portion and the groove bottom side portion is formed on the land portion, and the length of the inclined portion is changed in proportion to the length of the land portion. It is characterized by.

The operation of the pneumatic tire according to claim 1 will be described below. When a large input external force F is applied to the conventional block 112 having no inclined portion in the sipe 114 shown in FIG. 4A, the sipe neighborhood S of the block 112 divided by the sipe 114 is shown in FIG. As shown in the figure, the falling block rigidity decreases.

However, when a large input external force F is applied to the conventional block 112 in which the inclined portion 116A exists in the sipe 116 shown in FIG. 5A, the portions of the block 112 divided by the sipe 116 , FIG. 5 (B)
By overlapping at the inclined portion 116A shown in FIG.
A large fall of the sipe vicinity portion S of the block 112 can be suppressed, and a decrease in block rigidity can be prevented. However, conventionally, regardless of the size of the arranged blocks 112, the length of the inclined portion 116A is constant, and the suppression amount is different between the large pitch block and the small pitch block despite the falling amount. It was the same and the amount of suppression was not optimal.

On the other hand, the pneumatic tire according to the present invention is provided with a tread portion in contact with the road surface over one circumference, and a plurality of land portions are arranged on the tread portion along the circumferential direction of the tread portion. The structure is to be. Further, there are a plurality of types of the land portions having different lengths along the circumferential direction of the tread portion, and a sipe extending in a direction intersecting the circumferential direction of the tread portion is formed on the land portion. The sipe has an inclined portion between the surface portion of the land portion and the groove bottom portion, and the length of the inclined portion is changed in proportion to the length of the land portion. I have.

As a result, the shape of the sipe is improved so that the length of the inclined portion is changed in proportion to each pitch length of the block, so that the rigidity of the block is made uniform and the optimum shape of each block is achieved. As a result of obtaining the amount of suppression of the fall, the exercise performance of the tire was improved.

[0010] Specifically, in the conventional example employing a crank-shaped sipe of a certain size, the steering stability in a dry state is slightly inferior, but the steering stability in a dry state of the pneumatic tire according to the present invention is not improved. Had improved to an impeccable level. Further, even in the steering stability in a dry state, the block rigidity is further uniformed at the time of high-speed cornering in which a large input external force is applied, and it is possible to improve the exercise performance at the time of cornering. Also, the steering stability in a wet state has been improved as compared with the conventional example.

The operation of the pneumatic tire according to claim 2 will be described below. The present invention has a configuration similar to that of the first aspect and operates in the same manner, but further has a configuration in which the length of the land portion along the circumferential direction of the tread portion is 20 mm or more. . That is, in a pneumatic tire having a relatively large tread pattern, uniform block rigidity can be obtained, and the effect of improving exercise performance can be exhibited.

The operation of the pneumatic tire according to claim 3 will be described below. The present invention has the same structure as that of the first and second aspects and operates in the same manner. However, the length of the inclined portion is Y, and the tread portion on the land portion where the inclined portion of this length exists is provided. When the length of the land portion along the circumferential direction of X is X, the value of Y / X is in the range of 0.01 to 0.1.

In other words, when the value of Y / X becomes smaller than 0.01 due to the shortened slope, the effect of suppressing the falling of the block becomes insufficient. In addition, when the value of Y / X is greater than 0.1 due to the length of the inclined portion, the effect of suppressing the falling of the block is increased, but the tire is hardly removed from the vulcanization mold during tire production. Therefore, the wear of the vulcanization mold becomes severe, the maintenance life of the vulcanization mold is shortened, and the manufacturing cost is increased. Therefore, the value of Y / X is in the above range.

The operation of the pneumatic tire according to claim 4 will be described below. The present invention has the same configuration as that of claims 1 to 3 and operates in the same manner, but further has a configuration in which the inclination of the inclined portion is set to an angle in the range of 25 ° to 75 °. ing. That is, when the inclination angle of the inclined portion is larger than 75 °, the effect of suppressing the block from falling down becomes insufficient. In addition, the inclination angle of the inclined portion is 25 °.
If it is smaller than this, the effect of suppressing the falling of the block will be greater, but the tire will not easily fall out of the vulcanization mold during tire production, so the wear of the vulcanization mold will increase and the vulcanization mold will become severe. Maintenance life is shortened,
Manufacturing costs will increase. Therefore, the inclination angle of the inclined portion is set in the above range.

The operation of the pneumatic tire according to claim 5 will be described below. The present invention has the same configuration as that of the first to fourth aspects and operates in the same manner. However, the width dimension of the inclined portion along the circumferential direction of the tread portion is in the range of 1 mm to 9 mm. It has a configuration. That is, when the width of the inclined portion is shorter than 1 mm, the effect of suppressing the block from falling down becomes insufficient. Further, when the width of the inclined portion is longer than 9 mm, although the effect of suppressing the block from falling is increased, the tire is difficult to come off from the vulcanization mold during tire production. The wear becomes severe, the maintenance life of the vulcanizing mold is shortened, and the manufacturing cost is increased. Therefore,
The width dimension of the inclined portion is in the above range.

The operation of the pneumatic tire according to claim 6 will be described below. The present invention has the same configuration as that of claims 1 to 5 and operates in the same manner. However, the depth from the surface of the land portion to the far end of the inclined portion is D1, and the total depth of the sipe is Assuming that D0 is D0, the value of D1 / D0 is 0.3 to
0.5. That is, when the value of D1 / D0 is larger than 0.5, the effect of suppressing the falling of the block becomes insufficient.
If the value of 1 / D0 is less than 0.3, uneven wear is likely to occur, so the value of D1 / D0 is in the above range.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire according to one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a typical example of a tread pattern of a pneumatic tire 10 according to the present embodiment. Here, as for the internal structure of the pneumatic tire 10, as shown in FIG. 2, a carcass 12, which is a radial carcass, and a highly rigid belt (not shown) arranged to cover a crown portion of the carcass 12.
This type of pneumatic tire is a general combination of a tread 14 composed of tread rubber and disposed on the outer peripheral surface of the belt, and therefore will not be described in the following description.

Further, as shown in FIGS. 1 and 2, the tread 14 having an outer surface formed in an arc-shaped crown shape on the outer surface of the pneumatic tire 10 in contact with the road surface.
The shoulder portions 16 respectively form both end portions of the tread 14.

The tread 14 of the pneumatic tire 10 has a tread pattern shown in FIG. That is, the tread 1 which is the tread portion of the pneumatic tire 10
Along the central line CL, which is the equator plane of No. 4, a central block 20
Are arranged on the left and right sides of the center line CL, and a plurality of blocks 18 are arranged over the circumference of the tread 14 along the circumferential direction R of the tread 14. For this reason, a plurality of block rows composed of these blocks 18 are formed side by side in the tire width direction.

A deep groove 22 which is a deep groove is formed between the block 18 and the central block 20, and a shallow groove 24 which is a shallow groove is formed between the blocks 18. , Blocks 18, 20 are provided with inclined surfaces 26 formed obliquely from the top surfaces to the groove portions 22, 24.

Further, in the present embodiment, the tread 14
There are five types of blocks 18 having mutually different lengths along the circumferential direction R, and five types of pitches exist in the tread pattern in accordance with the differences in the lengths of the blocks 18. Specifically, as shown in FIG. 1, P1, P2, P
The pitches of P3, P4, and P5 are arranged in order, and these are repeated over the entire circumference of the tread 14.

On the other hand, the center line C
In the portion near L, sipe 28 as a narrow groove is provided so as to extend in a direction intersecting the circumferential direction R of the tread 14 two by two, and as shown in FIG. Between the upper part 28A which is the part of the sipe 28 and the lower part 28C which is the part of the sipe 28 on the groove bottom side.
An inclined portion 28B that is inclined along the circumferential direction R of the tread 14 is formed.

Then, as shown in FIG.
When the length of the block 18 along the circumferential direction R of the tread 14 in the block 18 in which the inclined portion 28B having the length Y exists is represented by X, the length X
Is 20 mm or more, and the value of Y / X is 0.01
The length Y of the inclined portion 28B is proportional to the length X of the block 18 so as to be in the range of 0.1. Further, the inclined portion 28B with respect to the surface of the block 18
When the inclination is α, the angle α is in a range of 25 ° to 75 °, and when the width of the inclined portion 28B is Z, the width Z is in a range of 1 mm to 9 mm. Further, when the depth from the surface of the block 18 to the far end of the inclined portion 28B is D1, and the total depth of the sipe 28 is D0,
The value of D1 / D0 is in the range of 0.3 to 0.5.

Next, the operation of the pneumatic tire 10 according to the present embodiment will be described below. The pneumatic tire 10 according to the present embodiment is provided with a tread 14 that is in contact with a road surface over one round, and a plurality of blocks 18 are arranged along a circumferential direction R of the tread 14 so as to form a tread 1.
4. Further, there are a plurality of types of the blocks 18 having different lengths along the circumferential direction R of the tread 14. A sipe 28 extending in a direction intersecting the circumferential direction R of the tread 14 is formed in the block 18. I have. The sipe 28 has an inclined portion 28B between an upper portion 28A on the surface side of the block 18 and a lower portion 28C on the groove bottom side, and has a length Y of the inclined portion 28B.
Is changed in proportion to the length X of the block 18.

As a result, the shape of the sipe 28 is improved so that the length Y of the inclined portion 28B is changed in proportion to the pitches P1, P2, P3, P4, P5 of the block 18, so that the block rigidity is improved. Each block 1 is made uniform
As a result, the pneumatic tire 10 was improved in kinetic performance.

On the other hand, in the present embodiment, the length X of the block 18 along the circumferential direction R of the tread 14 is set to 20 mm or more. That is, in the pneumatic tire 10 having the tread pattern in which the blocks are somewhat large as in the present embodiment, uniform block rigidity is obtained, and the effect of improving the exercise performance of the pneumatic tire 10 is sufficiently exhibited. it can.

Further, in this embodiment, the value of Y / X is in the range of 0.01 to 0.1, the inclination angle α of the inclined portion 28B is in the range of 25 ° to 75 °, and the inclined portion 28B Has a width Z in the range of 1 mm to 9 mm. That is,
When the inclined portion 28B becomes shorter and the value of Y / X becomes smaller than 0.01, the inclination angle α of the inclined portion 28B becomes 75 °.
When the width is larger than 1 mm, or when the width Z of the inclined portion 28B is shorter than 1 mm, the effect of suppressing the falling of the block 18 becomes insufficient and the exercise performance of the pneumatic tire 10 can be improved. Did not.

When the slope 28B becomes longer and the value of Y / X becomes larger than 0.1, when the slope α of the slope 28B becomes smaller than 25 °, or when the slope 28B When the width dimension Z is longer than 9 mm, although the effect of suppressing the falling of the block 18 is increased, the tire becomes difficult to come off from the vulcanizing mold during tire production, so that the wear of the vulcanizing mold is reduced. As a result, the maintenance life of the vulcanization mold is shortened, and as a result, the production cost increases, and it becomes difficult to produce the low-cost pneumatic tire 10. From the above, the value of Y / X, the inclination angle α of the inclined portion 28B
The width Z of the inclined portion 28B is set in the above range.

On the other hand, in the present embodiment, the value of D1 / D0 is in the range of 0.3 to 0.5 with respect to the depth of the inclined portion 28B. That is, if the value of D1 / D0 is larger than 0.5, the effect of suppressing the block 18 from falling down becomes insufficient, and if the value of D1 / D0 is less than 0.3, uneven wear easily occurs. , D1 / D0 are in the above range.

Next, the results of running tests in which the pneumatic tire described in the present embodiment is compared with the tire according to the conventional example will be described with reference to Tables 1 and 2 below. In other words, the pneumatic tire of the conventional example shown in Table 1 is provided with a crank-shaped sipe having an inclined portion having a fixed size regardless of the pitch of the block. The tire is provided with a sipe in which the size of the inclined portion is changed in proportion to the change in the pitch of the block. Then, a running test was performed with each of these tires mounted on a vehicle, and the results in Table 1 below were obtained.

[0031]

[Table 1]

That is, as shown in Table 1, the driving stability and the cornering stability in the dry state and the wet state were evaluated by running tests, and as a result,
In the conventional example using a crank-shaped sipe of a certain size,
Although the steering stability in the dry state was slightly poor at 6.0, in the example corresponding to the pneumatic tire 10 according to the present embodiment, the steering stability in the dry state was improved to a satisfactory level of 7.0. I was Further, even in the steering stability in a dry state, the block rigidity is further uniformed at the time of high-speed cornering in which a large input external force F is applied, and the exercise performance at the time of cornering can be improved. Also, the steering stability in a wet state has been improved as compared with the conventional example.

That is, the pneumatic tire of the example had a higher score in any of the evaluation items than the pneumatic tire of the conventional example, and it was found that the pneumatic tire of the example was superior to the conventional pneumatic tire. In addition, the evaluation method of the running test is a sensory evaluation by the driver, and the higher the score is, the better the evaluation is, the better the evaluation is. The size of the tire used in the running test is P205 / 55R.
The size of the rim was 7J-16, and the vehicle used in the running test was a small European sedan.

On the other hand, Table 2 shows that the numerical values of the above-mentioned lengths X, Y, angle α, width dimension Z, depths D1, D0 indicate the specified range for each of the five types of pitches P1, P2, P3, P4, P5. In addition to the sample of Example 1 of the pneumatic tire having the inclined portion contained therein, at least one of the samples of the conventional example and the sample having the inclined portion deviated from the numerical values of the dimensions and angles described above. Samples from Example 2 to Example 4 are shown.

[0035]

[Table 2]

Then, each of these tires was mounted on a vehicle and the same running test as shown in Table 1 was performed. As a result, the samples of the conventional example and the examples 2 to 4 were compared with the sample of the example 1. At least one of the evaluation items was insufficient, and some samples were difficult to manufacture. Specifically, in the second embodiment in which the value of Y / X is smaller than 0.01 as a result of the small value of the length Y, the block 18 is used.
The effect of suppressing the fall of the tire is insufficient, and the exercise performance of the pneumatic tire 10 cannot be improved. Also, if the angle α is 2
In Example 3 in which 15 ° was smaller than 5 °, and in Example 4 in which the value of Y / X was larger than 0.1 as a result of the large value of the length Y, the tire was removed from the vulcanizing mold when the tire was manufactured. Since it is difficult to remove the pneumatic tire 10, it is difficult to manufacture the pneumatic tire 10 at a low cost. Accordingly, it can be understood that Example 1 is superior to the conventional example and any of the samples from Example 2 to Example 4.

In the above embodiment, the pitch of the tread pattern is changed in accordance with the size of the blocks with five types of blocks, but the sizes of the blocks may be plural types other than the five types. good. Also,
The dimensions, angles, and the like are not limited to the dimensions exemplified in the above-described embodiment, but may be within the range of numerical values described in claims. Further, although two sipes are used in the above embodiment, one or three or more sipes may be formed in each block.

[0038]

Since the pneumatic tire of the present invention has the above-described structure, the pneumatic tire has an excellent effect that the exercise performance can be improved by improving the shape of the sipe and making the block rigidity uniform.

[Brief description of the drawings]

FIG. 1 is a development view showing a tread of a pneumatic tire according to one embodiment of the present invention.

FIG. 2 is a view taken in the direction of arrow 2-2 in FIG. 1;

FIG. 3 is a view taken in the direction of arrow 3-3 in FIG. 1;

FIG. 4 is a sectional view of a block of a first conventional example,
(A) is a diagram showing a state before an external force is applied, (B)
FIG. 4 is a diagram showing a state where an external force is applied.

FIG. 5 is a sectional view of a block of a second conventional example,
(A) is a diagram showing a state before an external force is applied, (B)
FIG. 4 is a diagram showing a state where an external force is applied.

[Explanation of symbols]

 Reference Signs List 10 Pneumatic tire 14 Tread 16 Shoulder part 18 Block 28 Sipe 28B Inclined part

Claims (6)

[Claims] 1. A pneumatic tire having a tread portion in contact with a road surface over one circumference, and a plurality of land portions arranged side by side along the circumferential direction of the tread portion on the tread portion. There are a plurality of types with different lengths along the circumferential direction of the tread portion, extending in the direction intersecting with the circumferential direction of the tread portion, and a portion between the surface side portion of the land portion and the groove bottom side portion. A pneumatic tire, wherein a sipe having an inclined portion is formed on the land portion, and the length of the inclined portion is changed in proportion to the length of the land portion. 2. The length of the land portion along the circumferential direction of the tread portion is
The pneumatic tire according to claim 1, wherein the thickness is 20 mm or more. 3. When the length of the slope portion is Y, and the length of the land portion along the circumferential direction of the tread portion in the land portion where the slope portion of this length exists is X, Y / X When the value is 0.01-0.
3. The pneumatic tire according to claim 1, wherein the pneumatic tire has a range of 1. 4. An apparatus according to claim 1, wherein the inclination of the inclined portion is set to an angle in a range of 25 ° to 75 °.
The pneumatic tire according to any one of the above. 5. The pneumatic tire according to claim 1, wherein a width dimension of the inclined portion along a circumferential direction of the tread portion is in a range of 1 mm to 9 mm. 6. When the depth from the surface of the land portion to the far end of the inclined portion is D1, and the total depth of the sipe is D0, D
The pneumatic tire according to any one of claims 1 to 5, wherein a value of 1 / D0 is in a range of 0.3 to 0.5.